Collaborative Research: Active, Upper Plate Deformation in Response to Migration of the Panama Triple Junction, Pacific Coast, Panama and Costa Rica

这项关于弧前演化的多学科研究考察了俯冲带上板块中短期(数年)和长期(数千至数百万年)的应变模式，该俯冲带横跨俯冲的巴拿马断裂带，巴拿马断裂带是一条活跃的转换断层。该项目的目标是检验若干假设，其中包括：1)上板块变形主要是与科科斯海脊碰撞有关的压痕构造的结果；2)菲拉-科斯特纳逆冲带随着巴拿马三重交汇的迁移而横向传播到巴拿马；3)上板块中的速度场反映了科科斯海脊碰撞，包括穿过菲拉-科斯特纳山脉的缩短、跨越巴拿马断裂带陆上投影的剪切/抬升以及与地震周期有关的弹性应变。研究小组正在利用构造分析、第四纪地质测绘和年代测定以及大地全球定位系统和模型研究，努力将长期变形记录与短期运动学指标结合起来，以便能够评估上板块的变形速度和样式。菲拉·科斯特纳冲断带前缘与火山碎屑扇的交汇为限制变形提供了极好的时间线。对布里卡半岛上一大批海洋阶地的放射性碳测年和光学激发发光测年，产生了该半岛第四纪晚期变形的极好记录。应变分配的大地测量研究将确定短期弹性应变的空间和时间模式。俯冲带是地球上最大的地震发生地，沿着板块边界积累弹性应变，直到在地震期间释放这些储存的能量。通过结合中美板块边界上板块的短期和长期变形指标，可以评估导致地震的弹性应变或可恢复应变，以及平均许多次地震影响的永久应变。该项目具体涉及哥斯达黎加南部和巴拿马西南部板块边界的耦合属性，并对这些地区的地震危险性进行了评估。该项目在宾夕法尼亚州立大学和三一大学首席研究人员的指导下，涉及研究生和本科生，并与哥斯达黎加和巴拿马的研究人员进行科学合作。该项目得到了NSF地球科学部构造计划和NSF国际科学与工程办公室的支持。

This multidisciplinary study of forearc evolution examines the short term (years) and long term (thousands to millions of years) patterns of strain in the upper plate of a subduction zone that straddles the subducting Panama Fracture Zone, an active transform fault. The project goals are to test several hypotheses, including: 1) upper plate deformation is primarily a consequence of indentation tectonics related to Cocos Ridge collision; 2) the Fila Costena thrust belt is propagating laterally into Panama with the migration of the Panama Triple Junction; 3) the velocity field in the upper plate reflects Cocos Ridge collision, including shortening across the Fila Costena, shear/uplift across the onshore projection of the Panama Fracture Zone, and the elastic strain associated with the earthquake cycle. The research team is using structural analyses, Quaternary geologic mapping and dating, and geodetic GPS and modeling studies in an effort to integrate a long-term record of deformation with short-term indicators of kinematics to allow for assessment of rates and styles of deformation of the upper plate. Intersection of the leading edge of the Fila Costena thrust belt with a volcanic debris fan provides excellent timelines to constrain deformation. Radiocarbon and Optically Stimulated Luminescence dating of a superb flight of marine terraces on the Burica Peninsula yield an excellent record of late Quaternary deformation of the peninsula. Geodetic research of strain partitioning will determine the spatial and temporal patterns of short-term elastic strain.Subduction zones are sites of the largest earthquakes on earth, with buildup of elastic strain along the plate boundary until release of this stored energy during earthquakes. By combining short-term and long-term indicators of deformation in the upper plate of the Middle America plate boundary, the elastic or recoverable strain that leads to earthquakes as well as the permanent strain that averages the effects of many earthquakes can be evaluated. This project specifically addresses the coupling attributes of the plate boundary in southern Costa Rica and southwestern Panama, with an assessment of the earthquake hazard of these regions. The project, under the direction of principal investigators from Pennsylvania State University and Trinity University, involves graduate and undergraduate students and scientific collaborations with Costa Rican and Panamanian researchers. The project is supported by the NSF Earth Sciences Division Tectonics Program and the NSF Office of International Science and Engineering.